The present invention relates to a laser diode marker for high speed cinematography which is more particularly used for the time marking of events.
It is known that high speed cinematography is a technique consisting of filming, by means of a suitable camera, an event having a very short duration, which can be a few dozen microseconds or less.
In order to study such an event, following the recording thereof on a photosensitive support or film with which the camera has been equipped, it is necessary to mark one or more particular instants, which are synchronous with the event, e.g. instants separated from one another by the same time interval, by marking the photosensitive support using light signals synchronous with these particular instants.
For this purpose, it is possible to use a device called a marker, which comprises a light-emitting diode, whose emitted radiation is in the near infrared range, associated with an electronic camera having a tube equipped with a photodiode of type S 20 or S 20R.
Such a marker suffers from the disadvantage of leading to pale and unusable recordings, bearing in mind the low radiance of the lighting source used and the fact that the photocathode used is only slightly sensitive to the near infrared.